President Barack Obama. AP Photo/Aaron Favila,Pool President Barack Obama fired off a series of tweets on Wednesday about why the US should and will accept some of the refugees trying to escape the violence in Syria.

"Welcoming the world's vulnerable who seek the safety of America is not new to us," he wrote. "We've safely welcomed 3 million refugees since 1975."

A wide swath of Republican presidential candidates and other leaders have sounded the alarm over Syrian refugees coming to the US after last week's terror attacks in Paris. One of the Paris attackers was reportedly carrying a Syrian refugee passport, though its authenticity has not been confirmed.

Obama's critics argue that accepting refugees could lead to similar massacres in the US. Real-estate mogul Donald Trump, the Republican presidential front-runner, even said Tuesday that the refugees could be "the ultimate Trojan horse" for terrorists.

But Obama countered by saying that any Syrian refugees in the US would have passed the "highest security checks," and that turning away the refugees would betray American values.